The secretory pathway in the guinea pig exocrine pancreas has been defined in the past in terms of H3-leucine incorporated into secretory protein (autoradiography and cell fractionation studies). Using a two- dimensional gel technique (isoelectric focusing followed by SDS gradient gel electrophoresis), the secretory pathway will be redefined on a protein specific basis. This will involve studies on (1) cell fractions taken at varying time points during a pulse-chase protocol using a mixture of fifteen C14 amino acids, and (2) radiolabeled secretion discharged into incubation medium from pancreatic lobules under varying conditions designed to favor evaluation of (a) discharge, (b) intracellular transport,and (c) the secretory pathway taken as a whole. Using mRNA derived from puromycin-high salt disassembly of bound polysomes from dog pancreas, the primary translation products obtained in vitro will be compared to radiolabeled secretion derived from pancreatic slices by SDS gradient gel electrophoresis and radioautography. Since preliminary studies suggest the presence of pancreatic precursors, attempts will be made using selective immunoprecipitation methods, to isolate several specific precursor- product pairs. Tryptic mapping and sequencing studies will be done on these pairs to determine if the additional peptide sequence is attached to the NH2 terminal end of the precursor molecule, as postulated by the "signal" hypothesis. Using direct cannulation of the pancreatic duct and the two- dimensional gel technique, exocrine proteins from the human pancreas will be characterized according to charge (isoelectric point), molecular weight, relative concentrations, and enzymatic function. Changes in relative concentrations and two-dimensional migration of proteins will be studied in response to (1) changes in diet, (2) changes in hormonal status, and (3) pancreatic disease states.